258 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
exigencies of their position, confined as they are by the papille, so 
that they lie frequently transversely with their narrow ends extend- 
ing downwards. (Fig. 2.) 
The ventral surface is characterized by the total absence of pig- 
ment, which is true of the corium as well as of the epithelium. 
ABNORMAL CONDITION OF THE SKIN. 
In two successive Springs I have observed certain tumours of the 
skin of a somewhat spongy appearance which do not appear to be 
confined to any particular region of the body but are commonest on 
the head and in its neighbourhood. I have, however, observed them 
on various parts of the trunk. It is possible that these are to be seen 
also at other times of the year, but, as they have only attracted my 
attention in Spring, I supposed at first that they might be somewhat 
similar to the ‘ Perlbildungen’ described by Leydig, or comparable - 
to the more extensive epidermal changes which take place at the 
breeding time in many Cyprinoids. That they are not frequent is 
sufficient indication that they are not normally recurring structures ; 
and Prof. Leydig informs me that the histological change is not of 
the same nature as that which characterizes the ‘ Perlbildung.’ 
Their appearance and the condition of their occurrence appear to me 
to exclude their being merely a reparative proliferation after a wound, 
and I have arrived at the opinion that we have in these tumours 
something similar to Epitheliomata. 
If a portion of such a tumour be placed in Miiller’s fluid over night 
and the epidermis pencilled away, the slender papille stand up from 
the corium so as to form a sort of pile on its surface. The dissocia- 
tion of the epidermis takes place much more readily than in normal 
skin, partly owing to the fact that the superticial layers, especially 
that bearing the cuticular border, have disappeared, partly owing to 
infiltration into the interepithelial spaces. The altered papille 
instead of being short, simple and cylindrical, may attain a length of 
over 1 mm., be much branched, and sometimes flattened and palm- 
ately branched. For the nourishment of the increased epidermal 
surface, the vascular networks of the papillze are much richer, and an 
increased number of pigment cells are observable. Although the 
papillary layer of the corium is thus increased in thickness, the 
fibrous layer is much thinner than in the neighbouring unaffected 
parts of the skin. The nature of the cells, which fill up the inter- 
